Furnace stoker



Sept 5, 1933 s. J. HENDERsHoTT 1,925,803

FURNACE STOKER Filed Sept. 2, 1930 3 Sheets-Sheet l ffm HMM www d` ATToRNEYs Sept. 5, 1933. s. J. HENDERsHoT-r FURNACE STOKER Filed Sept. 2, 1930 3 Sheets-Sheet 2 i INVENTOR .S 20,5 J/ZencZensZa- ATTORNEYA Sept. 5, 1933. s. J. HENDl-:RsHoTT FURNACE STOKER Filed Sept. 2, 1930 3 Sheets-Sheet 3 gmc/WDM Patented Sept. 5, 1933 UNITED STATES PATENT OFFICE FURNACE STOKER Application September 2, 1930. Serial No. 479,297

3 Claims.

The invention relates to automatic stokers for domestic heating furnaces and more particularly to the hopper construction and arrangement for controlling the operation of the Stoker.

One of the objects of the invention is to provide a construction for automatically indicating at a point remote from the furnace that the fuel hopper is becoming empty and requires more fuel.

Another object is to provide a safety device for automatically shutting off the stoker before all of the fuel in the hopper has been fed to the furnace thereby preventing furnace gases from travcling backward through the Stoker and entering the furnace room.

A further object is to provide a simple hopper construction for accomplishing the purposes set forth above.

In the drawings Figure 1 is an elevation partly in section of a furnace stoker embodying my invention;

Figure 2 is an end view of the stoker showin the hopper and the switch mechanism;

Figure 3 is a section on the line 3-3 of Figure 2;

Figure 4 shows a modified construction of control switch. Figure 5 is a semi-diagrammatic side view of a furnace illustrating the stoker mechanism and the controls, the switches 21 and 23 being diagrammatically shown opposite the hinge 23a for convenience in illustration.

In the construction as illustrated in the drawings, 1 ,represents a body portion or base above which is mounted the fuel hopper 2. The body 1 is hollow and is provided at the bottom thereof with a transversely extending screw conveyor 3 which projects outwardly from the body and is enclosed by a laterally projecting tube 4. This tube terminates inV an upwardly extending elbow portion 5 which rises within the center of the retort 6. 7 is a grate suitably mounted to surround the retort and to receive the coal or other solid fuel as it is fed upwardly into the retort. For driving the conveyor 3 there is an electric motor 8 connected to the conveyor through a suitable gear reduction mechanism 9 in the gear casing 10.

The stoker as described above is adapted'for intermittent feeding of coal or other fuel from the hopper 2 into the furnace and the intermittent motion of the screw conveyor 3 is provided by the starting and stopping of the electric motor 8. The control of the motor 8 is preferably effected by means of a thermostatic mechanism which may be of any suitable, type such as are commercially manufactured at thevpresent time. Thus in the electrical diagram as illustrated in Figures 4 and 6, 11 indicates diagrammatically a remote control thermostat which is electrically connected to a suitable controlling device 12 which in turn is connected to the stoker driving motor 8 and also to a furnace control motor 13. The furnace control motor 13 is of a suitable type to mechanically operate the furnace control mechanism such as the draft damper and the check damper. As diagrammatically illustrated in Figure 6, the arm 14 is connected to the check damper 14a and the arm 65 15 is connected to the draft damper 15a. These two arms 14 and 15 are eccentrically arranged with respect to the motor shaft 16 and are arranged 180 apart so that when the arm 14 is in its upper position the arm 15 is in its lower 70 position and vice versa. The electrical power is delivered to the controlling device 12 through y the line conductors 17 and 18 and the arrangement is such that when the temperature of the thermostat is below a predetermined amount, the electrical connections are completed to the stoker motor 8 causing the same to operate continuously and the electrical connections to the furnace control motor 13 are completed causing this motor to move a predetermined distance to move the arm 15 to its lower point and the arm 14 to its upper point and remain in these positions. Thus the draft 15a is operated and the check 14a is closed. When the temperature of the thermostat is above the predetermined point the electrical connections to the stoker motor 8 are broken thus stopping 'the motor and stoker, and the electrical connections to the furnace control motor 13 cause the same to move the arm 15 to its upper position and the arm 14 to its lower position, thus shut- 90 ting off the draft to the furnace and opening the check damper. This last condition of the motors 8 and 13 may be obtained by electrically connecting the conductors 19 and 20 together and is normally automatically effected by the thermostat 11 95 when temperature is above the predetermined setting. i

In accordance with my invention, I have provided an additional switch mechanism 21 connected between the conductors 19 and 20, the 100 arrangement being that the closing of this switch will de-energize the motor 8 to shut off the stoker mechanism and place the furnace in non-operating condition.

22 represents a signal light connected to the 105 line conductors 1'7 and 18 through a switch mechanism 23. The switches 21 and 23 are adapted t0 be operated when the fuel in the hopper 2 is below a predetermined amount and the arrangement is such that the switch 23 is actuated when- 110 Amust be refilled at the earliest opportunity. The

switch 21 is preferably arranged to be closed when the fuel has reached so low an amount as to make the further operation of the furnace undesirable and this switch acts as a safety device for preventing the operation of the stoker mechanism with an insufficient supply of coal in the hopper. The preferred construction of hopper Vfor accomplishing the purposes as above set forth is as follows:

The hopper 2 may be of any desired size but preferably is large enough to hold a supply of fuel suincient for at least several days normal operation of the furnace. As shown, the hopper is hingedly mounted on the base or body 1 by means of a pin 23a which extends through the hinge members 25 on the hopper. At the side of the hopper opposite the hinge members 25 a plate 27 is secured thereto'having two depending arms 28 extending below the top of the body member 1 and provided with laterally extending portions 29. The body 1 has laterally projecting lugs 30 extending over the portions 29. 31 is a spring inserted between a lug 32 on the hopper and a projecting portion 33 of the body member, the spring exerting an upward pressure on the hopper in opposition to the weight of the hopper and the load contained therein. The compression of the spring 31 may be suitably adjusted by means of the adjusting screw 34. The compression of the spring is such that when the hopper is completely filled with fuel, the spring is collapsed and the hopper 2 rests directly upon the body 1 but as the fuel is drawn from the hopper to the furnace the reduction in weight of the fuel in the hopper permits the spring to urge the hopper upwardly in opposition to gravity action.

The electrical switches 21 and 23 heretofore mentioned are preferably inserted between the laterally projecting portions 29 of the hopper and 30 of the body. Thus as shown, the switch 21 consists of a contact 35 on the body 30 and the contact 36 on the member 29. The switch 23 consists of a stationary contact 37 on the member 30 and a yieldable contact 38 on the member 29. 'I 'he yieldable contact 38 is slidable within a fibre bushing 39 in which is arranged a suitable spring 40. The fibre bushing 39 serves to insulate the contact Bilfrom` the supporting member 29 and similarly the contact 36 is insulated from the supporting member 29 by an insulating bushing 4l.

It will be noted that the cooperating contacts 37 and 38 of the switch 23 are arranged closer than the contacts and 36 of the switch 21 and therefore the switch 23 will be closed prior to the closing of the switch 21. In the operation of the device the compression of the spring 31 and the distance between the contacts is so arranged that the switch 23 will be actuated when the fuel in the hopper is low but still suiiicient to .operate the furnace for a predetermined time.

The contacts 35 and 36 are spaced further apart so that the switch 21 is not operated until a further lowering of the fuel takes place. Thus the signal 22 acts as a warning signal to notify the attendant that the fuel is low, whereas the switch 21 acts to automatically stop the stoker mechanism when the fuel in the hopper becomes so low as to render further operation of the stoker unsafe or inadvisable.

In the modified construction, as shown in Figure 5, the control mechanism is mounted in a separate container 43. The projecting portion 29 of the hopper is provided with an extension 44 projecting through an aperture 45 in the housing 43. Within the housing are two switch mechanisms, one preferably a mercury switch 46 and the other a mechanical switch 47. The mercury switch is adapted to control the electric current to the stoker motor 8. It may be of any suitable construction such as commercially available for this purpose. As shown, the mercury container 48 is carried by a rockable arm 49 pivoted at 50 to the housing 43. A lever 51 is pivoted co-axially therewith and has at one end a slot 52 for receiving a pin 53 on the extension 44. The other end of lever 51 is arranged to engage a cooperating contact member 55 which thereby completes a circuit 56 leading to the signal lamp 22, The circuit 56 is energized preferably by a transformer 57.

58 is a spring connected to pins 59 and 60 on the members 49 and 51 respectively. The spring is designed to give a snap action to the switch, being so arranged as to ride over the pivot point during the movement of the extension 44.

In the operation of the modified device4 the hopper when full of coal maintains the extension 44 and the switch mechanism in the positions shown in Figure 5. As the load on the hopper lightens it gradually moves upward due to the pressure of the spring 31, thereby moving the lever 51 about its pivot 50 until the lever contacts with -the cooperating elements thereby closing the switch and energizing the signal lamp 22. Further withdrawal of the coal from the hopper will raise the same higher until finally the line of action of the spring 58 will pass the pivot point 50. Immediately the arm 49 is pulled by the spring to its opposite position of adjustment, as shown in dotted lines, in which position the electric circuit is broken and the stoker motor therefore deenergized.

In the modifications above described, the invention has been embodied in different specific constructions but in each case the underlying idea is present. It will be apparent therefore that by means of our invention we obtain` in a Stoker mechanism for domestic furnace installation an arrangement which automatically indicates at a remote point whenever it is time to replenish the fuel in the hopper. Also the arrangement provides an automatic means for stopping the operation of the stoker whenever the coal supply in the hopper is below the predetermined point where safe automatic operation may be continued.

The thermostatic control mechanism may be of any well known type heretofore used and as diagrammatically illustrated in Fig. 5 is as follows: The control device 12 includes an electrical contact arm 12a which is actuated by the motor 13 through an angle of 180 between contacts 12b and 12. The thermostat 11 has a movable contact finger 11a which 'is actuated respectively by rise or fall in temperature between the contacts 11b and 11. The electrical circuit for the motor 13 includes conductors 13a and. 13b, the latter including the primary winding A of a choke coil. The secondary winding B of this choke coil is included in a circuit 11d leading from the thermostat 11 to the contact arm 12a and completed through the movable finger 11a and alternatively through the contacts 11b and 11, which latter are respectively connected to the contacts 12b and 12. Thus as shown inFig. 5 if the finger 11 is engaged with the contact 11, and the contact arm12 is engaged with the contact 12b, the circuit including the secondary winding B will be closed which will permit current to flow through the primary winding A to the motor 13, energizing the latter and rotating the crank shaft 16, which in turn moves the contact arm 12. This travels through 180, the circuit being maintained by a segmental contact 12d with which the contact 12 is engaged during its movement which closes a shunt 11 around the thermostatic switch 12, which when said arm is engaged with the contact 12 will couple contacts 12t and 128 which are in the electrical circuit 8 of the motor 8. This will energize the motor 8 as long as the contact arm 12a remains in this position, but when it is moved back to the contact 12b the circuit 8 will be broken, stopping the motor 8. This circuit 8a is also controlled by the switch 21 which as before stated is between the conductors 19 and 20. The conductor 20 has connected therein the electro-magnet 20a for operating circuit breaker 20b in the motor circuit 8, the arrangement being such that whenever the switch 21 is closed the circuit 8 is open. However, the specific arrangement of circuits just described is immaterial and forms no part of my invention, which includes within its scope any means for de-energizing the motor 8 whenever the hopper 2 is empty or nearly empty of fuel.

What I claim as my invention is: 1. A Stoker mechanism for domestic furnaces comprising a retort adapted to be inserted into a furnace, draft control means for said furnace, a fuel conduit connecting with said retort, a conveyor in said conduit, a driving motor for said conveyor, a fuel hopper pivoted to said conduit and communicating therewith, resilient means for urging said hopper upwardly about said pivot in opposition to the weight of the fuel therein, an electric switch operable in response to the reduction to a predetermined point of the weight of the fuel in said hopper, and means controlled by said switch for stopping said driving motor and closing said draft control means. 2. A stoker mechanism for domestic furnaces comprising a retort adapted to be inserted into a furnace, draft control means for said furnace, a fuel conduit connecting with said retort, a conveyor in said conduit, a driving motorf for said conveyor, a fuel hopper pivoted to said conduit and communicating therewith, resilient means for urging said hopper upwardly about said pivot in opposition to the weight of the fuel therein, a pair of electric switches successively operable by the movement of said hopper in response to the reduction to a predetermined point of the weight of fuel therein, a signal device connected to the first operated of said switches and means operable by the second operated of said switches for stopping said driving motor and closing said draft control means.

3. A stoker mechanism for domestic furnaces comprising a fuel-feeding device adapted to 'be inserted into a furnace, a hopper communicating with said device and movably mounted thereon, a conveyor -in said fuel-feeding device, a motor for driving said conveyor, resilient means for urging said hopper upwardly in opposition to the weight of the fuel therein, means for controlling the air to said furnace, an electric switch operable in response to the reduction to a predetermined point of the weight of the' fuel in said hopper and means controlled by said switch for stopping said driving` motor and closing said air control means.

SILAS J. HENDERSHOTI. 

